$\dfrac{6}{10} - \dfrac{2}{5} = {?}$
Answer: $ = {\dfrac{6 \times 1}{10 \times 1}} - {\dfrac{2 \times 2}{5 \times 2}} $ $ = {\dfrac{6}{10}} - {\dfrac{4}{10}} $ $ = \dfrac{{6} - {4}}{10} $ $ = \dfrac{2}{10}$